1. Field of the Invention
This invention relates to voltage-to-current (V-I) converters formed as part of an integrated-circuit (IC) on a monolithic chip. More particularly, this invention relates to such converters of the differential-input, differential-output type.
2. Description of the Prior Art
Voltage-to-current converters are employed in a number of different products such as analog multipliers and modulators. Several well known and extensively used analog multiplier circuits are shown for example in my U.S. Pat. No. 4,586,155. The accuracy of such analog multipliers is highly dependent upon the quality of the V-I converters forming part of the circuitry.
Prior art V-I converter circuits have had serious deficiencies which have adversely affected the performance of the multipliers or other components in which they are used. For example, complementarity of the two output currents of the converter has been inadequate ("complementarity" in this context refers to the degree to which the sum of the output currents remains constant with signal variations). Some converter circuits particularly have suffered from poor high-frequency accuracy, when the two output currents become severely unbalanced. Transient response has generally not been satisfactory, and the output signals develop both low-frequency and high-frequency distortions which need to be sharply reduced to achieve the desired component performance.